Fusarium root rot of peas: update and future research opportunities Syama Chatterton1, Robyne Bowness2 and Kan-

Fa Chang3 1AAFC-Lethbridge, 2,3 Alberta Agriculture and

Rural Development

Dry field peas • Increased production of field peas • 3.2 million acres harvested in

2012, increase of 35% • Yield decreased 16% to 32.1

bushels per acre in 2012 • Alberta – 960,000 acres planted,

935,000 acres harvested • Average yield = 40.7 bushels/acre,

decrease of 4.5%

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http://www.aitc.sk.ca/photogallery

Pea root rot complex • Important widespread diseases of field pea

• Can attack the crop at various growth stages, symptoms in seedlings to mature plants

• Problematic in Alberta during summers of 2010 and 2011 (above average moisture)

• Still a problem in 2012, despite hot, dry summer

– Cool, wet weather during seedling and hot, dry weather after seedling stage

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Root rots - Current disease situation • In Central Alberta surveys consistently find

very high incidence of root rot

• Increasing reports from producers about root rots in fields

• In Manitoba – 100% of field peas surveyed had root rot

– Variety of Fusarium spp.

• In Saskatchewan in 2012 – first reported incidence of the root rot pathogen, Aphanomyces euteiches

4 www.apsnet.org

Pea root rots • Complex of different soilborne pathogens

– Rhizoctonia solani, Fusarium spp. > F. solani f. sp. pisi

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F. avenaceum, F. oxysporum, F. redolens, F. graminearum

Root rot symptoms

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Photo courtesy of R. Bowness http://mtvernon.wsu.edu/path_team/

Brown, spreading lesions on taproots, root decay, and reddening of vascular tissue

Root rot field symptoms - early

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Photos courtesy of Kan-Fa Chang

Early season symptoms: - Poor emergence, seedling collapse, stunted growth

Root rot field symptoms - late

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Photos courtesy of Kan-Fa Chang

Late season symptoms: - Stunted growth, yellow patches, stand collapse

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Root rot impact on field pea • Interferes with nodulation,

nitrogen fixation

• Deteriorates the roots causing weak root system

• Reduces plant biomass

• Stunted growth, stand collapse after flowering, yellowing patches

• Yield losses are common

– Hard to measure

– Relate to disease severity

Photo courtesy of R. Bowness

Fusarium root rot pathogens • Produce long-lived resting spores

within soil

• Patchy distribution within a field

• Variation in aggressiveness of isolates

• Infections can occur throughout the growing season – roots grow through soil profile to meet resting spores

• Usually require plant stress for infection

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http://www.mycology.adelaide.edu.au

Photo courtesy of R. Bowness

Fusarium root rot management • Limited options within a season

• There are no cultivars resistant to root rot pathogens

• Manage disease before seeding

– High quality seed

– Cultural practices

– Reduce soil compaction and increase residue decomposition

ÿSeed treatments

ÿCrop rotation

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Fusarium root rot management • Seed treatment

– Ensures crop gets off to a good start – Prevents early infection – Mixed results on effect of late symptoms ÿPlanting into sites with a history of root

rots or poor stand establishment

• Crop rotation – Reduce resting-spore inoculum in soil – 4-year break between pulse crops – Problem with F. avenaceum?

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http://www.aitc.sk.ca/photogalle

Future research goals • Why is root rot increasing and what can we do about it? • Comprehensive field surveys of Alberta pea fields –

root and soil samples to see what’s present • Relationship between inoculum levels in soil and risk of

developing disease and yield loss – Risk assessment based on soil tests

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Future research goals • Seed treatments to reduce early infections, prevent

late symptom development

• Resistance screening of field cultivars

• Host range and survival of Fusarium spp.

• Soil conditions and soil management practices that will reduce survival of long-lived resting spores

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Thanks! Questions?

15 http://www.ndsu.edu/pubweb/pulse-info/fieldtext.html

Fusarium root rot of peas: update and future research opportunitiesDry field peas Pea root rot complexRoot rots - Current disease situationPea root rots Root rot symptomsRoot rot field symptoms - earlyRoot rot field symptoms - lateRoot rot impact on field peaFusarium root rot pathogensFusarium root rot managementFusarium root rot managementFuture research goalsFuture research goalsThanks! Questions?